I had never really appreciated how much trouble our relatively low powered WLAN devices could cause for RADAR. It turns out RADAR antennas have gigantic Gain numbers, and a very large number of side lobes - which I wouldn't have guessed for such a directional antenna.

Many documents list the relevant power levels and channel change rules, but I had never seen graphics that show the problem - and so clearly.

I wrote a blog post on weather radars and DFS (https://metis.fi/en/2017/01/weather-radars/). It didn't take me but a couple of days to get a screenshot of a interfering transmitter on a weather radar. It is so frequent. (And I didn't stare at the display for hours, I checked it occasionally.)

The radars use magnetrons to produce the signal. That's why the frequency tends to shift slightly. Magnetrons aren't as accurate as crystal oscillators used in Wi-Fi. The signal is typically kilowatts, because the reflections of the rain droplets is so weak. I had an interesting chat with a lady in our national meteorological institute. She was very happy to provide me information if it could help reduce the interference. I promised to spread the word.